Periodic Reporting for period 4 - ATTIDA (Attosecond space-time imaging of coherent quantum dynamics)
Periodo di rendicontazione: 2024-07-01 al 2025-06-30
Electron motion is at the heart of matter, technology and life and evolves on an extremely fast time scale known as the attosecond time scale (1 attosecond = 10^-18 seconds). In systems with a finite size, such as molecules and nanomaterials, this motion is in addition confined to spatial scales on the order of nanometers or less. This confinement enhances quantum effects and forces electrons to interact more strongly with each other. These dynamics are coherent, which means that they evolve according to the quantum wave nature of the electrons. However, the coherent effects last only up to tens of thousands of attoseconds due to the influence of the environment, making their detection very challenging. In order to observe these phenomena simultaneously in space and time, a new methodology is required. In this project, we address this challenge by developing two electron microscopy approaches, attosecond scanning tunneling microscopy (STM) and ultrafast low-energy electron holography (LEEH).
In attosecond STM, extremely short laser pulses illuminate a sample, such as a metallic surface or an organic molecule. In the course of our project ATTIDA, we have advanced attosecond STM through both theoretical and experimental studies. Most notable is the demonstration of attosecond currents and control of their direction solely through the waveform of intense infrared laser pulses, showing that ultrafast studies in STM with attosecond resolution are feasible. A second light source generating attosecond XUV pulses has been completed, which will open up molecular studies in the near future.
In the second approach, ultrafast LEEH, we use a beam consisting of extremely short electron pulses to probe electron dynamics inside a nanomaterial sample. The interaction with electrons inside the sample is imprinted on the electron beam, resulting in a spatially resolved image on a screen. In the course of ATTIDA, we have built a source of femtosecond electron pulses capable of nanometer and femtosecond resolution and studied its dynamics theoretically. Experiments with nanostructures are currently underway.
Both methods will enable us to record movies of the coherent electron dynamics, their evolution in space and time, and also to follow their decay. Our research does not only allow us to take a look into new physics at extremely short time scales but has also implications for technology
In attosecond STM, extremely short laser pulses illuminate a sample, such as a metallic surface or an organic molecule. In the course of our project ATTIDA, we have advanced attosecond STM through both theoretical and experimental studies. Most notable is the demonstration of attosecond currents and control of their direction solely through the waveform of intense infrared laser pulses, showing that ultrafast studies in STM with attosecond resolution are feasible. A second light source generating attosecond XUV pulses has been completed, which will open up molecular studies in the near future.
In the second approach, ultrafast LEEH, we use a beam consisting of extremely short electron pulses to probe electron dynamics inside a nanomaterial sample. The interaction with electrons inside the sample is imprinted on the electron beam, resulting in a spatially resolved image on a screen. In the course of ATTIDA, we have built a source of femtosecond electron pulses capable of nanometer and femtosecond resolution and studied its dynamics theoretically. Experiments with nanostructures are currently underway.
Both methods will enable us to record movies of the coherent electron dynamics, their evolution in space and time, and also to follow their decay. Our research does not only allow us to take a look into new physics at extremely short time scales but has also implications for technology
In 2020, the project ATTIDA was initiated at the Technion - Israel Institute of Technology. A team of physicists was formed to carry out the proposed research in a new laboratory. We have successfully designed and constructed an experimental setup for attosecond STM, overcoming several technical and physical challenges. We have explored the physics underlying the interaction of an ultrashort laser pulse with a metallic sample. Aided by a novel measurement method for laser-driven currents based on fast light waveform modulation, we have achieved a proof-of-principle demonstration of attosecond STM [D. Davidovich et al., preprint arXiv:2507.10252 (2025)]. Here, we induce STM tunnelling currents using two-color laser pulses and dynamically control their direction, relying solely on the sub-cycle waveform of the pulses. We observe non-adiabatic tunnelling with an electron current burst duration of 860 as. Despite working under ambient conditions but free of thermal artifacts, we achieve sub-angström topographic sensitivity and a lateral spatial resolution of 2 nm. This unprecedented capability to control the direction of attosecond electron tunneling bursts will enable triggering and imaging ultrafast charge dynamics in atomic, molecular and condensed systems at the spatio-temporal microscopy frontier of lightwave electronics. Our study has been made possible by our newly developed theory models [B. Ma et al., Phys. Rev. Lett. 133, 236901 (2024); A. Borisov et al., ACS Photonics 12, 2137 (2025); B. Ma et al., preprint arXiv:2503.14531 (2025)]. We also developed and built an experiment capable of delivering attosecond extreme-ultraviolet light pulses [Z. Chen et al., ACS Photonics 12, 2819 (2025)], which will open the door to molecular studies.
Furthermore, we have realized a source of ultrashort electron pulses for ultrafast low-energy electron microscopy inside a dedicated experimental setup placed in ultrahigh vacuum. A theory investigation shows that record-short electron pulses with a duration of a few thousand attoseconds are expected at the point of interaction with a nanomaterial sample, which promises excellent temporal resolution [M. Eldar et al., J. Phys. B 55, 074001 (2022)]. We also devised a new way to measure the temporal structure of femtosecond and attosecond electron pulses [Z. Chen et al., Science Advances 9, adg8516 (2023)]. Lastly, our research on low-energy electrons inspired a theory study of their resonant interactions with light, which revealed their unique physics and may open up applications in quantum simulations [M. Eldar et al., Phys. Rev. Lett. 132, 035001 (2024)].
Furthermore, we have realized a source of ultrashort electron pulses for ultrafast low-energy electron microscopy inside a dedicated experimental setup placed in ultrahigh vacuum. A theory investigation shows that record-short electron pulses with a duration of a few thousand attoseconds are expected at the point of interaction with a nanomaterial sample, which promises excellent temporal resolution [M. Eldar et al., J. Phys. B 55, 074001 (2022)]. We also devised a new way to measure the temporal structure of femtosecond and attosecond electron pulses [Z. Chen et al., Science Advances 9, adg8516 (2023)]. Lastly, our research on low-energy electrons inspired a theory study of their resonant interactions with light, which revealed their unique physics and may open up applications in quantum simulations [M. Eldar et al., Phys. Rev. Lett. 132, 035001 (2024)].
The scientific community has a longstanding dream: the ultimate microscope that is not just able to resolve tiny objects in space, as in a static image, but also to observe their fast dynamics on their natural time scale using ultrafast photonics. For electrons, this means simultaneous nanometer/angström spatial resolution and femtosecond/attosecond temporal resolution, an extremely challenging endeavor. The scanning tunneling microscope (STM) is the go-to approach to achieve atomic resolution of a wide range of systems but is limited to picosecond and femtosecond time resolution. In ATTIDA, we have significantly progressed beyond the state of the art by performing an experimental demonstration of attosecond currents and the waveform control of their direction in an STM. This brings ultrafast quantum tunneling to the nano-scale, bringing the scientific community closer to the ultimate microscope. Our groundbreaking theory studies, complementary to the experiments, elucidate the physics of electrons tunneling through nanometric vacuum gap on attosecond scales. We believe that our models will be a guide to many scientists to design and interpret their experiments. In the near future, we will apply our approach to enter the molecular realm.
Also towards the second approach, ultrafast low-energy electron microscopy, we have made significant progress beyond prior research. Our pulsed electron source supports a temporal resolution far better than the state of the art, which will enable insights into ultrafast charge dynamics in nanomaterials. In addition, our theory works propose new approaches to generate and measure ultrashort electron pulses and study their interactions with light in the low-energy regime.
Also towards the second approach, ultrafast low-energy electron microscopy, we have made significant progress beyond prior research. Our pulsed electron source supports a temporal resolution far better than the state of the art, which will enable insights into ultrafast charge dynamics in nanomaterials. In addition, our theory works propose new approaches to generate and measure ultrashort electron pulses and study their interactions with light in the low-energy regime.